1. Field of the Invention
The present invention relates to a keyboard apparatus in which a whippen of an action unit is pivoted by key depression.
2. Description of the Related Art
Conventionally, a keyboard apparatus having action units has been known. For example, Japanese Laid-open Patent Publication No. 2003-263152 discloses action units for upright piano in which hammer shanks are vertically disposed to enable hammers to strike respective ones of strings which are vertically stretched.
Since the action units for upright piano have hammer shanks disposed vertically, the height size of the action units is relative large. Nevertheless, no substantial efforts have been made to reduce the height size of the action units. In grand pianos where hammer shanks are originally disposed laterally, no substantial improvement for reduction of the height size of action units has been made.
Action units have whippens each of which is generally configured to be driven by a corresponding one of keys through a capstan attached to a rear end portion of the key. A driven point where the whippen is in contact with the capstan is located between a whippen pivot fulcrum and a key fulcrum as viewed in a front-to-rear direction.
Since the whippen is pivoted in a direction opposite to a pivot direction of the key in a key depression stroke, the capstan and the driven point are slidingly moved relative to each other by a large amount in the front-to-rear direction. Such a whippen drive state, which is not optimum from the viewpoint of drive efficiency, is noticeable especially in an upright piano since the whippen pivot fulcrum is located far above the key fulcrum. In other words, there is a room to improve the height size of action units and to improve the whippen drive state. However, there are strict design restrictions in an upright piano, making it difficult to achieve improvements.